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MIX‐cAMP signaling in 3T3‐L1 preadipocyte differentiation
Author(s) -
Gabrielli Matias,
Martini Claudia,
Romero Damián,
Carmen Vila María
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.lb116
Subject(s) - adipogenesis , protein kinase a , 3t3 l1 , signal transduction , protein kinase b , endocrinology , chemistry , cellular differentiation , microbiology and biotechnology , medicine , oil red o , adipocyte , transcription factor , phosphorylation , biology , biochemistry , adipose tissue , gene
Adipogenesis is stimulated in 3T3‐L1 fibroblasts by a combination of insulin, dexamethasone (DEX), and methylisobutylxanthine (MIX). Mitotic clonal expansion (MCE) precedes differentiation of 3T3‐L1 fibroblasts to adipocytes. MIX increases cAMP content, which activates protein kinase A (PKA). However, PKA‐independent cAMP signaling through EPAC (exchange protein activated by cAMP) has also been reported. We found that H89, a PKA inhibitor, blocks MCE but not differentiation of 3T3‐L1 fibroblasts. Differentiation, evaluated by Oil‐Red‐O staining or quantification of triglycerides, did not occur when MIX was not present in the differentiation mixture but it was restored by addition of either dibutyryl‐cAMP (db‐cAMP) or 8‐CPT‐2‐Me‐cAMP. The latter activates EPAC but not PKA signaling. Furthermore, we found that MIX, db‐cAMP or 8‐CPT‐2‐Me‐cAMP increased PPARγ, a transcription factor required for adipocyte differentiation. PI3K‐PKB signaling is known to be required for differentiation. We found that insulin but not MIX, alone or in combination with insulin+DEX, was able to increase PKB phosphorylation. These results suggest that MIX signaling through cAMP‐EPAC, which is independent of PI3K‐PKB signaling, is also required for 3T3‐L1 fibroblasts differentiation to adipocytes. Supported by National Agency for Scientific and Technological Promotion (Argentina) BID‐PICT: 08–1826.